Labels have been used extensively on articles which are to be sold to indicate the price and/or the identity of the articles such as a stock number. Uniform product codes (UPC) are frequently placed on labels or directly on goods to identify the goods. Transferring price and identification labels from one item to another is a constant problem faced by store-owners, especially in retail areas where customers may switch labels to pay a lower price for the goods.
Label integrity also is vital in the pharmaceutical industry. Switched labels or mis-marked products can cause devastation or fatal results. Counterfeiting of products, and black market resale of original equipment parts are continuing problems. Accordingly, there is a need to permanently mark automotive parts in order to control the use of stolen parts in auto repair work and reduce auto theft.
Labels with vehicle identification numbers (VIN) can readily be produced, but such labels also can be readily removed without in any way damaging the part. Stamping of metal parts with the VIN is prohibitively expensive, and where a part is a thin metal part, such stamping operation may not be undertaken without damaging the part. Thus, there is a need for a practical way to mark automobile parts with identification numbers in such a way that the part can be readily identified with a particular automobile owner, and the marking is not readily removable.
Numerous label designs for tamper-proof labels have been described which provide an indication of the authentification. U.S. Pat. No. 5,042,842 (Green et al) employs a multilayer label consisting of a lower sheet of safety paper and an upper sheet. The lower sheet of safety paper is attached by a permanent adhesive to a product, and the upper sheet is attached by a patterned adhesive layer to the lower safety paper layer. Graphics, price information and variable serial numbers or model numbers can be printed on the top of the upper sheet. Indicia of authentication are printed on the bottom surface of the upper sheet. Authentication requires that the upper portion of the label including the upper sheet be separated from the lower safety paper sheet. Once separated, the layers cannot be rejoined to reconstitute the label. In addition, removal of the top portion is required in order to tell if an additional label has been placed over the top of the upper portion of the label.
U.S. Pat. No. 5,346,738 (Samonides) describes an identification label containing a microencapsulated etchant. The identification label is useful for marking a metal or other etchable surface such as an automobile part with an identifying indicia. The label comprises a protective cover sheet, a pressure-sensitive adhesive irremovably affixed to the cover sheet, and a liner with a release coating removably affixed to the adhesive. An identifying indicia comprising an etchant in a visible vehicle such as a printing ink is printed on the adhesive at the interface of the removable liner and the adhesive so that when the liner is removed, the remaining portions of the label will be adhesively attached to the metal surface with the etchant of the identifying indicia in etching contact therewith. The identifying indicia will thus be etched into the surface of the part for a permanent marking of the part.
U.S. Pat. No. 5,346,259 (Mocilnikar et al) describes a tamper-proof label comprising a thicker support material and a thinner fragile portion. The label is formed of a plurality of layers of varnish, adhesive, plastic and ink. The label incorporates an authentication region in which the text can be readily deciphered only with a special viewer. The top surface of the label can be written on with ink and is difficult to erase without destroying the fragile portion of the label. The label is adhered to a product by an adhesive which becomes aggressively bonded to the product over a relatively short period of time. In addition, the adhesive leaves a residue which is visible when illuminated with ultraviolet light.